Electronic devices with biased guide rails

This application is a continuation of international patent application No. PCT/US2021/042078, filed Jul. 16, 2021, which claims the benefit of U.S. provisional patent application No. 63/057,216, filed Jul. 27, 2020, which are hereby incorporated by reference herein in their entireties.

This relates generally to electronic devices, and, more particularly, to head-mounted electronic devices.

Electronic devices may contain components mounted in a housing. Head-mounted devices have structures that allow these devices to be worn on the heads of users.

A head-mounted device may be provided with displays. Lenses may be provided to allow a user to view images on the displays. A left optical module may be provided that includes a left display and left lens and a right optical module may be provided that includes a right display and right lens.

To support and guide the optical modules, the optical modules may be slidably mounted to guide rails. Positioners may be used to move the optical modules towards and away from each other along the guide rails to adjust the head-mounted device to accommodate different user interpupillary distances.

Each optical module may have portions configured to form openings or other structures that receive the guide rails. The openings may be, for example, cylindrical openings for receiving cylindrical guide rails. The guide rails may be biased against the surfaces of the cylindrical openings and/or other portions of the optical modules using springs or other biasing systems. By using the biasing systems, misalignment between the optical modules can be maintained within desired limits, while permitting the optical modules to slide along the guide rails during interpupillary distance adjustments.

If desired, guide rail sensors may be used to monitor the positions of the guide rails. In some configurations, the optical modules may be coupled to the guide rails using kinematic mounts.

An electronic device may have input-output devices for gathering input and providing output. These devices may include optical components such as cameras, displays, and lenses.

A top view of an illustrative electronic device is shown in. Electronic deviceofmay be a head-mounted device or other suitable device. As shown in, devicemay have a housing such as housing. Housing, which may sometimes be referred to as a housing wall, external housing, housing structures, enclosure, or case, may be formed from materials such as polymer, glass, metal, crystalline materials such as sapphire, ceramic, fabric, foam, wood, other materials, and/or combinations of these materials.

Devicemay have any suitable shape. Housingmay, for example, be configured to form a head-mounted housing in the shape of a pair of goggles (e.g., goggles having optional head straps such as strapsT, a nose bridge portion in nose bridge region NB that is configured to fit over a user's nose and help support housingon the user's nose, etc.) and/or other head-mounted structures. Housingmay separate interior regionfrom exterior region. Housingmay include portions such as front portion (front wall)F on front face F of device, rear portion (rear wall)R on opposing rear face R of device, and sidewall portions such as sidewall portionsW on sides W that extend between front portionF and rear portionR, so that housingencloses interior region.

Electrical and optical components may be mounted within housing(e.g., in interior region). As an example, housingmay have optical components in interior regionsuch as displaysand lenses. Displaysand lensesmay be mounted in optical modules(sometimes referred to as lens barrels, display and lens support structures, etc.). Images from displaysmay be viewable from eye boxesthrough lenses. A left display and left lens in a left optical modulemay be used to present a left-eye image to a user's left eye in a left eye boxand a right display and right lens in a right optical modulemay be used to present a right-eye image to a user's right eye in right eye box. Manual adjustment mechanisms and/or electrically adjustable actuators(e.g., motors or other electrically adjustable positioners) may be used to move optical moduleshorizontally across the front of the user's face (e.g., to adjust distance D between modulesalong a direction parallel to the X-axis or nearly parallel to the X-axis of). Optical modulesmay, for example, be moved closer to each other or farther apart from each other as needed to accommodate different user interpupillary distances.

A schematic diagram of an illustrative electronic device is shown in. Deviceofmay be operated as a stand-alone device and/or the resources of devicemay be used to communicate with external electronic equipment. As an example, communications circuitry in devicemay be used to transmit user input information, sensor information, and/or other information to external electronic devices (e.g., wirelessly or via wired connections) and/or may be used to receive such information from external electronic devices. Each of these external devices may include components of the type shown by deviceof.

As shown in, electronic devicemay include control circuitry. Control circuitrymay include storage and processing circuitry for supporting the operation of device. The storage and processing circuitry may include storage such as nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitrymay be used to gather input from sensors (e.g., cameras) and other input devices and may be used to control output devices. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors and other wireless communications circuits, power management units, audio chips, application specific integrated circuits, etc. During operation, control circuitrymay use display(s)and other output devices in providing a user with visual output and other output.

To support communications between deviceand external equipment, control circuitrymay communicate using communications circuitry. Circuitrymay include antennas, radio-frequency transceiver circuitry, and other wireless communications circuitry and/or wired communications circuitry. Circuitry, which may sometimes be referred to as control circuitry and/or control and communications circuitry, may support bidirectional wireless communications between deviceand external equipment (e.g., a companion device such as a computer, cellular telephone, or other electronic device, an accessory such as a point device, computer stylus, or other input device, speakers or other output devices, etc.) over a wireless link. For example, circuitrymay include radio-frequency transceiver circuitry such as wireless local area network transceiver circuitry configured to support communications over a wireless local area network link, near-field communications transceiver circuitry configured to support communications over a near-field communications link, cellular telephone transceiver circuitry configured to support communications over a cellular telephone link, or transceiver circuitry configured to support communications over any other suitable wired or wireless communications link. Wireless communications may, for example, be supported over a Bluetooth® link, a WiFi® link, a wireless link operating at a frequency between 10 GHz and 400 GHz, a 60 GHz link, or other millimeter wave link, a cellular telephone link, or other wireless communications link. Devicemay, if desired, include power circuits for transmitting and/or receiving wired and/or wireless power and may include batteries or other energy storage devices. For example, devicemay include a coil and rectifier to receive wireless power that is provided to circuitry in device.

Devicemay include input-output devices such as devices. Electronic components such as input-output devicesmay be used in gathering user input, in gathering information on the environment surrounding the user, and/or in providing a user with output.

Devicesmay include one or more displays such as display(s). Display(s)may include one or more display devices such as organic light-emitting diode display panels (panels with organic light-emitting diode pixels formed on polymer substrates or silicon substrates that contain pixel control circuitry), liquid crystal display panels, microelectromechanical systems displays (e.g., two-dimensional mirror arrays or scanning mirror display devices), display panels having pixel arrays formed from crystalline semiconductor light-emitting diode dies (sometimes referred to as microLEDs), and/or other display devices.

Devicesmay also include cameras. Camerasmay include visible light cameras, infrared cameras, and/or cameras that are sensitive at multiple wavelengths, may include three-dimensional camera systems such as depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices that capture three-dimensional images), may include time-of-flight cameras, and/or may include other cameras. Camerasmay face toward the user of deviceand/or away from the user of device.

Sensorsin input-output devicesmay include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors such as a touch sensor that forms a button, trackpad, or other input device), and other sensors. If desired, sensorsmay include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, fingerprint sensors, iris scanning sensors, retinal scanning sensors, and other biometric sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors such as blood oxygen sensors, heart rate sensors, blood flow sensors, and/or other health sensors, radio-frequency sensors, optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors, humidity sensors, moisture sensors, gaze tracking sensors, electromyography sensors to sense muscle activation, facial sensors, interferometric sensors, time-of-flight sensors, magnetic sensors, resistive sensors, distance sensors, angle sensors, and/or other sensors. In some arrangements, devicemay use sensorsand/or other input-output devicesto gather user input. For example, input-output devicessuch as buttons may be used to gather button press input, touch sensors overlapping displays can be used for gathering user touch screen input, touch pads may be used in gathering touch input, microphones may be used for gathering audio input (e.g., voice commands), accelerometers may be used in monitoring when a finger contacts an input surface and may therefore be used to gather finger press input, etc.

Input-output devicesmay include optical components such as depth sensors (e.g., structured light sensors or other sensors that gather three-dimensional image data), optical proximity sensors, ambient light sensors (e.g., color ambient light sensors), optical time-of-flight sensors and other sensorsthat are sensitive to visible and/or infrared light and that may emit visible and/or infrared light (e.g., devicesmay contain optical sensors that emit and/or detect light). For example, a visible-light image sensor in a camera may have a visible light flash or an associated infrared flood illuminator to provide illumination while the image sensor captures a two-dimensional and/or three-dimensional image. An infrared camera such as an infrared structured light camera that captures three-dimensional infrared images may have an infrared flood illuminator that emits infrared flood illumination and/or may have a dot projector the emits an array of infrared light beams. Infrared proximity sensors may emit infrared light and detect the infrared light after the infrared light has reflected from a target object.

If desired, electronic devicemay include additional components (see, e.g., other devicesin input-output devices). The additional components may include haptic output devices, actuators for moving movable structures in device, audio output devices such as speakers, light-emitting diodes for status indicators, light sources such as light-emitting diodes that illuminate portions of a housing and/or display structure, other optical output devices, and/or other circuitry for gathering input and/or providing output. Devicemay also include a battery or other energy storage device, connector ports for supporting wired communication with ancillary equipment and for receiving wired power, and other circuitry.

To help maintain desired alignment between optical modulesas optical modulesare moved by actuators(), optical modulesmay be mounted on optical module guiding structures such as guide rails or other elongated support members. This type of arrangement is shown in the top view of deviceof. As shown in, optical modulesmay be slidably coupled to guide railsto allow modulesto move horizontally (e.g., laterally along the X-axis to accommodate different user interpupillary distances).

Guide railsmay have circular cross-sectional shapes (e.g., guide railsmay be cylindrical rods) or may have other cross-sectional shapes. Guide rodsmay be formed from metal, polymer, and/or other materials. Hollow and/or solid members may be used in forming guide rods. To help reduce friction between guide rodsand optical modules, guide rodsand/or mating portions of modulesmay, if desired, be provided with a low-friction coating (e.g., nickel, etc.).

Guide railsmay span the width of housing. There may be left and right guide railsin devicethat are joined at a housing support structure aligned with nose bridge portion NB or left and right guide railsmay be formed as integral portions of a single guide rail member that extends across housing. Railsmay be straight or may, if desired, have a slight bend at nose bridge portion NB (e.g., to rake the left and right sides of the guide rails backwards slightly to conform to the shape of a user's face). As shown in the rear view of deviceof, there may be upper and lower guide railson the left and right of devicesuch as upper guide railT and lower guide rail. Arrangements with fewer guide rails or more guide rails may be used, if desired.

is a side view of an illustrative optical modulemounted on guide rails. In the example of, optical modulehas an upper portion such as portionT and a lower portion such as portionB. PortionsT and/orB may be integrally formed with main supporting structureM of the lens barrel structures and/or other support structures of optical moduleand/or may be separate members that are coupled (e.g., using welds, fasteners, adhesive, etc.) to main supporting structureM. Lensmay be aligned with displayso that an image on displaymay be viewed through lensfrom eye box.

As shown in, optical modulemay have portions that receive and couple to guide railswhile allowing optical moduleto slide along guide rails. For example, upper portionT may have a guide rail opening (optical module opening)such as openingT that receives upper guide railT and lower portionB may have a guide rail opening such as openingB that receives lower guide railB. OpeningsT andB may by cylindrical openings with circular cross-sectional shapes that receive the cylindrical members forming railsT andB and/or may have other shapes that partly or fully surround railsT andB.

To prevent railsfrom becoming stuck in guide rail openingsof optical module, the inner diameter of optical module openings may be slightly larger (e.g., by 2-50 microns, at least 5 microns, less than 100 microns, or other suitable amount) than the outer diameter of rails. To prevent excess motion, which could lead to misalignment of optical modules, devicemay be provided with guide rail biasing systems. The guide rail biasing systems may have movable biasing members (e.g., pins, plates, spherical members, hemispherical members, etc.) and biasing elements that apply force to the biasing members. The biasing elements may be, for example, springs such as coil springs, leaf springs, and/or other spring members, may be compressed polymer (e.g., elastomeric material, foam, etc.), may be magnets, and/or may be other biasing components that can be used to bias the biasing members in a desired direction.

Using the guide rail biasing systems, guide railsmay be pushed towards desired positions within openingsto help remove undesired play between guide railsand openings. As an example, guide railsmay be pressed against the inner surfaces of openings(e.g., at a location on the side of openingsthat faces eye boxesrather than the opposing side of openingsthat faces outwardly away from the user) and/or may be pressed against a structure mounted within openingssuch as a pin or other support member.

Consider, as an example, the cross-sectional side view of optical module portionB of. As shown in, portionB may have an opening such as openingB that receives lower guide railB. Lower guide rail biasing systemB may have a lower guide rail biasing element such as lower guide rail biasing elementB (e.g., a spring) and a corresponding movable biasing system member such as biasing memberB (e.g., a pin with a hemispherical head) and/or systemB may be formed from other biasing structures (e.g., a leaf spring, compressed foam, etc.). Under pressure from biasing elementB, memberB may press in directionagainst an adjacent surface of guide railB (e.g., the side of railB facing biasing systemB and facing away from the user). Pinmay be mounted on an opposing side of openingB. As a result of the force imposed on guide railB in direction, guide railB may bear against member(or, if desired, the inner surface of openingB) at contact location(e.g., a location on the surface of openingB facing the user and eye boxes). This creates a well-defined location for guide railB relative to the structures of optical moduleand helps prevent railB from moving excessively in the Y and/or Z dimensions within openingB, thereby helping to ensure that optical moduleis aligned satisfactorily with respect to eye box. Additional friction and resistance to sliding of optical modulealong the X axis is created by the use of biasing systems such as biasing systemB of, but when it is desired to move optical moduleswith respect to each other to adjust their spacing to accommodate a user interpupillary distance, sufficient force along the X dimension can be applied to overcome this friction.

If desired, springB and biasing elementB may be located on opposite sides of guide railB. Consider, as an example, the illustrative configuration of biasing systemB that is shown in. In this configuration, biasing systemB has a biasing memberwith a portion that forms biasing elementB. Biasing membermay be attached to portionB of optical moduleusing an attachment mechanism such as screwor other fastener. Screwmay have a threaded shaft or other structure that is fixedly attached to portionB. The shaft of screwmay be received within a slot in member. The slot may extend parallel to the Y axis ofto allow biasing memberto slide back and forth parallel to the Y axis.

A biasing element such as springB (e.g., a compression spring or other biasing spring) may be used to bias memberin the −Y direction. SpringB may have a first end that presses against a surface of membersuch as surfaceand an opposing second end that presses against a surface of portionB such as surface. When memberis moved in direction, springis compressed. Springthereafter presses against surfaceand biases the portion of memberthat forms elementB in directionrelative to portionB. This causes memberto contact railB at contact locationand to thereby bias the opposing side of railB against pinat contact location.

Membermay be formed from one or more materials. For example, membermay be formed from a metal (e.g., aluminum, stainless steel, etc.). The metal may be covered with a hard low-friction coating such as an electroless nickel coating to enhance wear resistance. As another example, membermay be formed from a polymer (e.g., a low-friction composite polymer filled with carbon fibers, fiberglass fibers, or other fibers). The low-friction composite polymer may be formed from a polymer such as PEEK (polyether ether ketone) or other polymer (e.g., a polymer that may be shaped by a molding process such as injection molding).

The examples ofdemonstrate how lower guide railB may be provided with an associated guide rail biasing system (illustrative systemB). If desired, upper guide railsT may also be provided with guide rail biasing systems. As shown in the cross-sectional side view of upper portionT of optical module, optical modulemay have biasing systemsT-andT-. SystemT-may have biasing elementT-for forcing movable biasing memberT-against an adjacent surface of guide railT in direction(or may have other biasing structures such as a leaf spring, compressed foam, etc.). SystemT-may have biasing elementT-for forcing movable biasing memberT-against an adjacent surface of guide rail(or may have other biasing structures sch as a leaf spring, compressed foam, etc.). Using systemsT-andT-, guide railT may be biased leftward so that the surface of guide railT contacts the inner surface of openingT at nominal biasing location(e.g., a location on the surface of openingT that faces the user and the eye boxes associated with device). The force of gravity tends to pull downwardly (in the −Z direction of) on guide railT. To compensate for the force of gravity and thereby ensure that locationis located on the left side of guide railT (facing the user and eye box) as shown in, biasing elementT-may be stronger than biasing elementT-.

During operation of device, a user's face and/or other external objects may impose forces on optical modules. This gives rise to a potential for three different types of misalignment between the left and right optical modules in device.

Rotation of optical modulesabout the X axis, which may sometimes be referred to as splay, may cause a first type of misalignment in which one image appears at a different height than the other image. For example, splay may rotate the left eye image from the left optical module up relative to the left eye box while rotating the right eye image from the right optical module down relative to the right eye box.

Rotation of optical modulesabout the Y axis, which may sometimes be referred to as image rotation, may produce a second type of misalignment in which the left and/or right images from modulesto appear tilted relative to the horizon. For example, the left eye image may be rotated counterclockwise and the right eye image may be rotated clockwise.

Another type of misalignment that may arise between optical modulesrelates to rotation of one or both of optical modulesabout the Z axis. This type of misalignment, which may sometimes be referred to as vergence, may be characterized by situations in which the left and/or right optical module points too far to the left or right in the X-Y plane.

All of these types of misalignment are preferably maintained at low levels (e.g., below +/−0.5°, below +/−0.4°, below +/−0.3°, or below +/−0.2°, as examples). In some situations, splay is the most undesired type of misalignment for users, so minimization of splay may be particular helpful in enhancing user comfort.

The use of guide rail biasing systems such as the illustrative biasing systems ofmay help minimize optical module misalignment. When biasing systemsT-andT-perform satisfactorily, the left optical module will be biased against upper railT at a location such as locationofand will be biased against lower railB at a location such as locationofor, whereas the right optical module will likewise be biased against upper railT at a location such as locationofand will be biased against lower railB at a location such as locationofor. In this case, both the left and right optical modules will have the same position relative to guide railsT andB and there will be no splay. A potential for splay may arise when stress from a drop event or other unexpected excessive force causes a biasing system to fail.

Consider, as an example, a worse case splay scenario in which biasing systemT-in the left optical module fails due to excessive force and in which biasing systemT-in the right optical module fails due to excessive force. Although this type of asymmetric failure changes the biasing locations of the left and right optical modules, the biasing arrangement ofhelps prevent undesired splay from arising. Failure of biasing systemT-in the left optical module will cause guide railT in the left optical module to be positioned against the inner surface of openingT at location, whereas failure of biasing systemT-in the right optical module will cause guide railT in the right optical module to be positioned against the inner surface of openingT at a different location such as location.

In the example of, systemT-is located at an angle A=+45° relative to the Y axis and systemT-is located at an angle A=−45° relative to the Y axis. When systemsT-andT-are operating satisfactorily, guide railT will therefore press against the inner side wall of openingT at location. When openingT in the left optical module contacts railT at locationwhile openingT in the right optical module contacts railT at location, both the left and right optical modules will be positioned more to the right (in the orientation of) than when in their desired nominal biased position. Lower guide rodB is biased satisfactorily at locationwith respect to lower optical module portionB for both the left and right optical modules (in this example). As a result, both the left and right optical modules will tip forward slightly (rotating a small amount about the X axis), under outward pressure from the user's face. Although both the left and right optical modules tilt forward in this way, the amount of tilt of the left optical module, which is dictated by the lateral displacement of railT experienced when railT contacts openingT at position, is equal to the amount of tilt of the right optical module, which is dictated by the lateral displacement of railT experienced when railT contacts openingT at position. No splay will therefore result. Because the configuration of the biasing systems oftends to prevent splay from arising, this configuration may sometimes be referred to as a splay-optimized or splay-immune biasing scheme. Other biasing schemes may be used, if desired (e.g., schemes for the upper guide rail that have more biasing systems per optical module, schemes with fewer biasing systems per optical module, schemes in which the biasing systems press in different directions such as the +Z direction, −Y direction, etc.). The configuration ofis illustrative.

show how a kinematic mounting scheme may be used to couple guide railsand optical modules. As shown in, upper guide railsT may be biased in the −Y direction by biasing system. Biasing systemmay include biasing elementand movable biasing memberthat contacts an adjacent portion of guide railT and pushes guide railT in directionor may include other biasing structures (e.g., a leaf spring, compressed foam, etc.). Biasing systemmay have a biasing element such as biasing elementthat pushes biasing member(e.g., a cylindrical pin) in directionuntil motion of memberis stopped by stop structures. Biasing systemmay have a biasing element such as biasing elementthat pushes biasing memberin directionuntil motion of memberis stopped by stop structures. In this configuration, guide railT is biased into contact with memberat known locationand into contact with memberat known location. Lower guide railB may be biased to known locationusing a biasing system such as systemB ofor.

is a rear view of optical modulewith this type of kinematic rail mounting arrangement. As shown in, there may be two of biasing systemsin portionT of moduleand two of biasing systemsin portionT of modulein addition to two of biasing systems. This establishes a first pair of known contact locations towards the right end of railT (e.g., a first locationand a first location) and, establishes a second pair of known contact locations at a different location along the length of railT such as towards the left end of railT (e.g., a second locationand a second location). In lower portionB, the location of optical module relative to guide railB is established at known location. Determining these five known locations on optical modulewhere railscontact module(e.g., two locationsin upper portionT, two locationsin upper portionT, and one locationin lower portionB), helps constrain five of the six degrees of freedom for motion of modulerelative to railsand the other support structures of device. The sixth degree of freedom (motion along the X axis) is not constrained except by operation of actuator, so that actuatormay be used to adjust the X-axis location of moduleto accommodate different user interpupillary distances.

If desired, control circuitrymay use one or more sensorsto monitor the location of optical modules. If misalignment is detected, corresponding action can be taken. For example, positioners may be adjusted to correct for the misalignment, image data for a display and/or camera may be warped to compensate for misalignment, alerts may be provided to the user and/or others, etc.

An illustrative optical module sensor system is shown in.is a perspective view of an illustrative guide rail position sensor. Sensorofhas a biasing member such as leaf spring memberwith a protruding portion such as portion. Strain gaugemay be coupled to memberand may be monitored by control circuitryto detect bending in member. As shown in, sensorofmay be attached to optical modulewith a fastener such as screwor other attachment mechanism so that protruding portionprotrudes into openingand into contact an adjacent surface of guide rail. Changes in the position of guide railwill result in changes in the detected strain by sensor, so sensorcan monitor the position of guide railrelative to optical modulealong axis. If desired, additional sensors such as sensormay be located at additional positions about rail(see, e.g., illustrative orthogonal position′ of, which allows position measurements along axis).

As described above, one aspect of the present technology is the gathering and use of information such as information from input-output devices. Such information may include personal data. The present disclosure contemplates that the entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal data will comply with well-established privacy policies and/or privacy practices. In particular, such entities should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal data private and secure.

In accordance with an embodiment, a head-mounted device is provided that includes a head-mounted support structure having left and right guide rails, and left and right optical modules mounted for sliding motion on the left and right guide rails, respectively, the right optical module has a first biasing system that presses against the right guide rail in a first direction and has a second biasing system that presses against the right guide rail in a second direction, and the left optical module has a third biasing system that presses against the left guide rail in a third direction and has a fourth biasing system that presses against the left guide rail in a fourth direction.

In accordance with another embodiment, the left optical module includes a left lens and a left display that provides a left eye image viewable through the left lens from a left eye box, and a right lens and a right display that provides a right eye image viewable through the right lens from a right eye box.

In accordance with another embodiment, the left and right optical modules are separated by a distance and the left and right optical modules are configured to slide along the left and right guide rails to adjust the distance.

In accordance with another embodiment, the head-mounted device includes an additional left guide rail and an additional right guide rail, the left optical module is mounted to the additional left guide rail for sliding motion and the right optical module is mounted to the right guide rail for sliding motion.

In accordance with another embodiment, the left optical module includes a fifth biasing system configured to press against the additional left guide rail and the right optical module includes a sixth biasing system configured to press against the additional right guide rail.